DANVILLE (AP) — The removal of a 2,500-ton deposit of coal ash in the Dan River from a spill in North Carolina has begun in Danville.

The toxic sludge measuring 350-by-20-yards and about 1 foot deep collected at the Schoolfield Dam after the massive Feb. 2 spill. Work began Monday and should be completed in late June.

The city’s water treatment plant also captured more than 250 tons of coal ash.

The coal ash removed from the river will be transported to a landfill in North Carolina’s Person County for permanent storage, according to published reports.

A collapsed pipe at Duke Energy’s Eden, North Carolina, power plant led to the spill of 39,000 tons of coal ash that polluted 70 miles of the Dan River. Danville is about 20 miles downstream.

Duke Spokesman Jeff Brooks said the coal ash at the dam is the largest deposit Duke has found that is a candidate for removal. The removal involves vacuuming the coal ash, sediment and water from the Dan River, before the water is separated and returned to the river.

“We’re trying to be minimally invasive,” he said of the operation.

The contractor is using so-called silt barriers to control the coal ash while it’s being pulled from the river bottom.

The dredging system is capable of collecting up to 1,500 gallons of coal ash, water and sediment per minute, Brooks said.

Officials anticipate transporting several dozen tons of coal ash per day from the site to the landfill in Person County.

Duke also plans to clean up a 40-ton coal ash deposit at Town Creek, 2 miles downstream. That project is supposed to be complete around the same time the Schoolfield project is expected to end, Brooks said.

Barry Dunkley, Danville Utilities’ division director for water and wastewater treatment, said the water treatment plant will close its water intake valve when dredging is taking place. It will be opened in the evening and operate overnight when there is no dredging.

Water treatment manager Alan Johnson said water sampling will continue through the dredging.

Officials have said the city’s treated water exceeds safe-drinking water standards.